ES2805322T3 - Layered structure with copper passivator - Google Patents

Abstract

Cable comprising a copper conductor and a polymeric layer adjacent to the copper conductor, wherein the polymeric layer comprises a polymeric composition comprising an ethylene polymer, comprising a comonomer with silane group-containing units that are hydrolyzable, and a benzotriazole compound.

Description

DESCRIPTION

Layered structure with copper passivator

Sector of the invention

The present invention relates to a cable comprising a copper conductor and a polymeric layer adjacent to the copper conductor, more specifically, to a cable or wire insulation layer that can preserve the copper conductor from fading. The polymeric layer adjacent to the copper conductor comprises a polymeric composition comprising an ethylene polymer, comprising a comonomer with silane group-containing units that are hydrolyzable, and a benzotriazole compound. This prevents discoloration of the copper conductor.

Prior state of the art

A typical power cable or wire generally comprises one or more conductors in a cable core, which is surrounded by one or more layers or sheaths of polymeric material insulation. The core is normally copper or aluminum, surrounded by a series of different polymeric layers, each of which fulfills a specific function, for example a semiconductor layer (protective layer), an insulation layer, a shielding layer of tape metallic and a polymeric cover. Each layer can provide more than one function. A low voltage cable or wire is often surrounded by a single polymeric layer that serves as an insulator, metallic shielding, and a polymeric covering layer. A medium to extra high voltage cable can be surrounded, for example, by a first polymeric semiconductor layer, a polymeric insulating layer, a second polymeric semiconductor layer, a metal tape shield and a polymeric jacket.

A wide variety of polymeric materials have been used as electrical semiconductor and insulating materials for power cables. Such polymeric materials, in addition to having adequate dielectric properties, must also be durable and must substantially retain their initial properties for effective and safe performance over many years of service. These materials must also meet the strict safety requirements established in international standards.

Power cables typically use stranded copper or aluminum conductors, although small power cables can use solid conductors.

Despite competition from other materials, copper remains the preferred electrical conductor in many electrical cable constructions, with the important exception of overhead electrical power transmission, where aluminum is often preferred. Copper wire is used in power generation, power transmission, power distribution, telecommunications, electronic circuits, and countless types of electrical equipment. Electrical wiring is the most important market for the copper industry. This includes building wire, communication wire, power distribution wire, appliance wire, automotive wire and wire, and magnetic wire. About half of all the copper mined is used to make electrical wire and cable conductors. Many electrical devices depend on copper wiring, due to its multitude of inherent beneficial properties, such as its high electrical conductivity, tensile strength, ductility, creep resistance (deformation), corrosion resistance, low thermal expansion, high thermal conductivity, weldability and ease of installation.

Copper reacts slowly with atmospheric oxygen to form a layer of brown-black copper oxide which, unlike the rust that forms when iron is exposed to humid air, protects the underlying copper from further corrosion. A green layer of verdigris (copper carbonate) can often be seen in old copper constructions. Furthermore, copper is sensitive to sulfur-containing substances, which contribute to discoloration, as well as fingerprints, as perspiration is corrosive. Discoloration of the copper conductor is a common problem. This impairs the aesthetic properties of the copper conductor. By connecting the copper conductor, the polymeric layers are removed to obtain a non-discolored part of the copper conductor. Many copper conductors are installed underground in the presence of water, which increases discoloration.

Patent US6262151 discloses the use of phenolic derivatives that include a benzotriazole group as UV absorbing agents for polyolefins.

The benzotriazole compound (including its derivatives) reduces the discoloration of copper on the copper surface. It is sold for that purpose. If the benzotriazole compound is applied to a copper surface, it will protect the surface from discoloration. It will form a protective polymeric benzotriazole-copper network. The protective layer will physically protect the copper from discoloration. The copper conductor can be easily scratched and the protective surface of the benzotriazole compound can be destroyed resulting in a discolored surface. This can happen when cable insulation is extruded onto the copper conductor or during cable installation or use. Commonly, copper passivators, for example the benzotriazole compound, are added to the copper conductor drawing oil prior to cable extrusion, thereby forming a thin layer of copper passivator on the surface of the copper conductor. However, this procedure does not lead to satisfactory protection against copper discoloration when the copper conductor comes into contact with moisture after cable extrusion.

The benzotriazole compound and its derivatives are commonly used in transformer insulating oils. It works as a corrosion inhibitor and protects copper. There is a positive correlation between the thickness of the passivating copper layer and the effectiveness in preventing corrosion.

Patent WO2014 / 177153 A1 discloses an electric cable, in particular for low voltage applications. The electrical cable comprises at least one conductive cable surrounded by insulation, in which the insulation is made of a thermoplastic material comprising - at least, approximately 0.01% by weight of component A selected from oligomeric hindered amines HALS types having a molecular weight of from about 500 to about 3,400; - at least about 0.01% by weight of component B selected from UV stabilizers comprising at least one sebacate residue substituted with at least one R1 and optionally R2, in which R1 means 1,2,2,6,6-pentamethyl-4-piperidinyl or 2,2,6,6-tetramethyl-4-piperidinyl and R2 means methyl or 1,2,2,6,6-pentamethyl-4- piperidinyl; - at least about 0.01% by weight of component C selected from hindered phenolics comprising a benzotriazole residue and having a molecular weight of from about 200 to about 500 and - at least 0 About 1% by weight of a source of calcium carbonate.

Furthermore, it is already known that a cable jacket composition contains 100 parts of resin and 0.05-10 parts of porous inorganic material containing a volatile Cu corrosion inhibitor (WPI DATABASE week 197439, Thomson Scientific, London , Great Britain; Patent AN 1974-68421V and Patent JP S49 10943 A (FURUKAWA ELECTRIC CO LTD) January 30, 1974 (01-30-1974)).

Furthermore, a separate marine sensing instrument cable has already been disclosed. It is prepared by extruding bleach- and UV-resistant ethylene propylene rubber insulation layers at the peripheries of tinned and annealed stranded copper conductors to form insulation wire cores (WPI DATABASE Week 201401, Thomson Scientific, London, Great Britain; AN 2013-J68331 and CN 102969948 A (JIANGSU YUANYANG DONGZE CABLE GROUP CO L) March 13, 2013 (03-13-2013) Patent EP1309632 B1 refers to a highly active condensation catalyst suitable for crosslinking of alkoxysilanyl polyolefins, for example, polyethylene with silane functional groups, selected from the group consisting of: (i) an alkylated aryldisulfonic acid selected from the group consisting of structure (I) and structure (II), in the that each of R1 and R2 is the same or different and is a linear or branched alkyl group with 6 to 16 carbons, and is 0 to 3, z is 0 to 3, provided that yz is 1 to 4, X is u n divalent residue selected from the group consisting of -C (R3) (R4) -, wherein each of R3 and R4 is H or, independently, a linear or branched 1-4 carbon alkyl group and n is 1; -C (= O) -, where n is 1, -O- where n is 1; -S-, where n is 1 to 3; and -S (O) 2-, where n is 1; (ii) a derivative of (i) selected from the group consisting of anhydrides, esters, epoxide-blocked sulfonic acid esters, acetylates, and amine salts thereof, which is hydrolyzable to alkylated aryldisulfonic acid.

Characteristics of the invention

The present invention is a cable comprising a copper conductor and a polymeric layer adjacent to the copper conductor, wherein the polymeric layer comprises a polymeric composition comprising an ethylene polymer, comprising a comonomer with silane groups containing units that they are hydrolyzable, and a benzotriazole compound.

A conductor can conduct electricity along its length. It can be a feed or signal stream. Polymers are defined by having more than at least 1000 repeating units.

Surprisingly, it has been discovered that a polymeric layer, comprising a polymeric composition comprising an ethylene polymer, comprising a comonomer with silane group-containing units that are hydrolyzable, and the benzotriazole compound, adjacent to a copper conductor, will form a protective layer on the copper conductor and will prevent discoloration of the copper conductor. Instead of applying the benzotriazole compound first on the surface of the copper conductor and risking scratching or damaging the surface during the application of the adjacent polymeric layer, the benzotriazole compound, which is present in the polymeric composition hereof The invention, surprisingly, migrates from the polymer composition to the surface of the copper conductor and forms a protective layer after the copper conductor is covered by the polymeric layer comprising the polymer composition comprising the benzotriazole compound. Some of the unreacted benzotriazole compound will remain in the polymeric layer and migrate as necessary. The polymeric layer will function as a reservoir for the benzotriazole compound, which prolongs the fading effect compared to direct application on the surface of the copper conductor. The protective layer will self-repair and the polymeric layer will function as a reservoir.

Benzotriazole is a compound with a benzotriazole active site. It can be substituted or unsubstituted. The layer polymeric means that the conductor is partially laminated or more suitably surrounds the conductor, i.e. the conductor is coated with a polymeric layer. The polymeric layer can be an insulation layer, a semiconductor layer, a combined insulation and cover layer. The decisive thing is that the polymeric layer must be adjacent to the conductor, that is, in direct contact. The polymeric layer is suitably an insulation layer or a combined insulation and cover layer, most suitably just an insulation layer. The insulation layer can be used in many applications that most suitably include copper conductors in a cable.

The cable of the present invention comprises a copper conductor and a polymeric layer adjacent to the copper conductor, wherein the polymeric layer comprises a polymeric composition comprising the ethylene polymer, comprising a comonomer with silane groups containing units that are hydrolyzable, and the benzotriazole compound. Suitably, the polymeric layer of the cable is an insulation layer, a semiconductor layer, a covering layer or a combined insulation and covering layer, more suitably an insulation layer or a combined insulation and covering layer. Most suitably, the polymeric layer is an insulating layer that is suitably lined with a cover layer.

Detailed description of the invention

The benzotriazole compound may be substituted or unsubstituted and is suitably a compound of formula (I) (hereinafter, benzotriazole compound):

(I) in which

R1 is a hydrogen atom, an alkyl group comprising at least 6 carbon atoms, suitably at least 12 carbon atoms, and suitably less than 100 carbon atoms, most suitably, of 12 to 100 carbon atoms, or an alkyl group comprising at least one amine group and

R2 is a hydrogen atom or an alkyl group, suitably a methyl group.

By substituting the benzotriazole compound, the balance between exudation and the compatibility between the polymer composition and the benzotriazole compound can be controlled. The improved solubility of the benzotriazole compound means that a higher loading of the benzotriazole compound can be added to the polymer composition.

Examples of commercial benzotriazole compounds are Irgamet 30, Irgamet 39, Irgamet 42, Irgamet BTA, Irgamet BTZ and Irgamet TTZ supplied by Basell.

In a further embodiment, the benzotriazole compound is substituted with at least one amine. Suitably, the benzotriazole compound is Irgamet 39, which is a mixture of 2 isomers: N, N-bis (2-ethylehexyl) -4-methyl-1H-benzotriazole-1-methylamine (CAS No.: 80584-90 -3) and N, N-bis (2-ethylehexyl) -5-methyl-1H-benzotriazole-1-methylamine (CAS No.: 80595-74-0).

In one embodiment, the amount of the benzotriazole compound in the polymer composition is 50 ppm to 1000 ppm, suitably 50 ppm to 500 ppm, or more suitably 100 ppm to 400 ppm. The polymer composition comprises an ethylene polymer. The ethylene polymer is suitably at least 70% by weight or more suitably more than 90% by weight of the polymer composition. The ethylene polymer suitably has an MFR2 of 0.1 to 40 g / 10 min, suitably 0.5 to 15 g / 10 min, and most suitably 0.75 to 4 g / 10 min.

The definition of ethylene polymer is a polymer with more than 50% by weight of ethylene monomers, suitably more than 90% by weight of ethylene monomers. The ethylene polymer may further comprise alpha-olefins and comonomers with vinyl groups and functional groups, such as polar comonomers.

The ethylene polymer comprises a comonomer with silane group-containing units that are hydrolyzable. Silane groups that are hydrolyzable mean that a silanol condensation reaction can form covalent bonds with other silane groups. Silane groups can form covalent bonds with other silane groups of the ethylene polymer with a comonomer with units containing silane groups and form a network. The degree of crosslinking can be measured, for example, by gel content or hot elongation.

The ethylene polymer with silane group containing units suitably has a silane content of 0.1 to 10% by weight, suitably 1 to 5% by weight 20, and most suitably, 1.5 to 3% by weight.

The ethylene polymer with silane group-containing units can be produced by various conventional procedures. Silane is hydrolyzable, that is, crosslinkable. Hydrolyzable silane groups can be introduced into the ethylene polymer by copolymerization of, for example, ethylene monomers with one or more comonomers containing silane groups or by grafting, i.e. by chemical modification of the ethylene polymer by the addition of silane groups, primarily, in a radical reaction, well known in the art. The benefits of copolymerization are that there is no residual polar peroxide or unreacted vinyl silanes in the final article. This will make the final product more uniform, of better consistency, and improve quality. The storage stability of ethylene copolymerized with vinyltriethoxysilane and / or vinyltrimethoxysilane produced in a high pressure radical process is greatly improved compared to grafted solutions. Another benefit is less handling of liquid vinyl silanes, which are flammable and have a strong odor. Other benefits are less rejects, less scorch (premature crosslinking in the extruder) and longer production cycles (less cleaning of the extruders). Copolymerization is the preferred production process of the ethylene polymer with units containing silane groups. The amount of silane groups can be decreased compared to grafting. The reason for this is that all the silane groups copolymerize whereas the graft polymer generally contains silane unreacted with peroxide residues. Suitably, the ethylene polymer with silane group-containing units is a low density ethylene polymer containing silane group-containing units.

The ethylene polymer of the present invention is produced by polymerizing ethylene, suitably, with a comonomer with silane group-containing units, as defined above, in a high pressure radical polymerization (HP) process. High Pressure) using free radical polymerization in the presence of one or more initiators and, optionally, using a Chain Transfer Agent (CTA) to control the MFR of the polymer.

The HP reactor can be, for example, a well known tubular reactor or autoclave, or a mixture thereof, suitably a tubular reactor. High pressure polymerization (HP) and adjustment of process conditions to further tailor the other properties of the polyolefin depending on the desired end application are well known and have been described in the literature, and can be easily used by a skilled. Suitable polymerization temperatures range up to 400 ° C, preferably 80-350 ° C, and pressure 70 MPa, preferably 100-400 MPa, more preferably 100-350 MPa. High pressure polymerization is generally carried out at pressures of 100 to 400 MPa and at temperatures of 80 to 350 ° C. These procedures are well known and well documented in the literature.

The incorporation of the comonomer with units containing silane groups (as well as other optional comonomers) and the control of the comonomer feed to obtain the desired final content of said comonomer (hydrolyzable) with units containing silane groups can be carried out in a known manner and is within the skills of a person skilled in the art.

More details on the production of ethylene homopolymers and copolymers by high pressure radical polymerization, among others, can be found in Encyclopedia of Polymer Science and Engineering, vol. 6 (1986), pp. 383-410 and Encyclopedia of Materials: Science and Technology, 2001 Elsevier Science Ltd .: "Polyethylene: High-pressure, R. Klimesch, D. Littmann and F.-O. Mahling pp. 7181-7184.

The silane group-containing comonomers for the copolymerization of silane groups or the silane group-containing compound for grafting silane groups to produce an ethylene polymer is suitably a vinyl silane compound represented by the formula:

R ¹ SiR ^2q Y ^3-q (II)

in which

R ¹ is an ethylenically unsaturated hydrocarbyl, hydrocarbyloxy or (meth) acryloxyhydrocarbyl group, each R ² is independently a saturated aliphatic hydrocarbyl group, Y, which may be the same or different, is a hydrolyzable organic group and q is 0, 1 or 2.

Special examples of unsaturated silane compounds are those in which R ¹ is vinyl, allyl, isopropenyl, butenyl, cyclohexanyl, or gamma- (meth) acryloxypropyl; Y is methoxy, ethoxy, formyloxy, acetoxy, propionyloxy, or an alkyl or arylamino group; and R ² , if present, is a methyl, ethyl, propyl, decyl, or phenyl group. The most suitable is vinyltriethoxysilane (VTES) or vinyltrimethoxysilane (VTMS).

One embodiment of the present invention is the copolymerization of the ethylene monomer with a vinyltriethoxysilane or vinyltrimethoxysilane comonomer in a high pressure radical process to produce the ethylene copolymer with a copolymer with silane group-containing units.

The ethylene polymer with silane group-containing units may further contain one or more comonomers that are different from the silane group-containing comonomer. Furthermore, the ethylene polymer with silane group-containing units may contain additional polar groups other than the silane groups (herein specification, called polar groups). In one embodiment, the ethylene polymer with silane group-containing units also contains polar groups, which can be introduced by grafting a compound containing polar groups or by copolymerizing a comonomer containing polar groups (herein referred to as a polar comonomer). In this embodiment, the ethylene polymer is produced by polymerizing ethylene monomer with comonomer containing silane groups and with at least one polar comonomer, suitably one.

In one embodiment, the ethylene polymer with silane group-containing units is selected from a polymer consisting of ethylene monomer, silane group-containing comonomer, and one or more polar comonomers, suitably one. Typical polar comonomers are a) vinyl carboxylate esters, such as vinyl acetate and vinyl pivalate, (b) (meth) acrylates, such as methyl (meth) acrylate, ethyl (meth) acrylate, (meth) butyl acrylate and hydroxyethyl (meth) acrylate, (c) olefinically unsaturated carboxylic acids, such as (meth) acrylic acid, malic acid and fumaric acid, (d) derivatives of (meth) acrylic acid, such as (meth) acrylonitrile and (meth) acrylamide, and (e) vinyl ethers, such as vinylmethyl ether and vinylphenyl ether. The ethylene polymer is produced by high pressure polymerization with free radical initiation.

Typical polar comonomers can be one or more hydroxyl groups, alkoxy groups, carbonyl groups, carboxyl groups, ether groups or ester groups, or a mixture thereof, can be used. More suitably, one or more polar comonomers containing one or more carboxyl and / or ester groups can be used as said polar comonomer. Even more suitably, the polar comonomers are selected from the groups of acrylates, methacrylates or acetates, or any mixture thereof. Even more suitably, they are selected from the group of alkyl acrylates, alkyl methacrylates or vinyl acetate, or a mixture thereof. More preferably, said optional polar comonomers can be selected from C1 to C6 alkyl acrylates, C1 to C6 alkyl methacrylates or vinyl acetate.

Especially suitable polar comonomers are vinyl acetate (EVA), methyl (meth) acrylate, (EMA and EMMA), ethyl acrylate (E ^and A) and / or butyl acrylate (EBA), most suitable, EBA, EMA and EEA. Two or more of these olefinically unsaturated compounds can be used in combination. The term "(meth) acrylic acid" is intended to encompass both acrylic acid and methacrylic acid. Ethylene copolymer is produced by high pressure polymerization with free radical initiation.

In one embodiment of the present invention, the polymeric layer is an insulating layer crosslinked by a condensation reaction of the ethylene polymer with a comonomer with units containing silane groups. Suitably, the condensation reaction is catalyzed by a condensation reaction catalyst. Typical cables with the insulation layer adjacent to the copper conductor are commonly thin and are used in applications exposed to weather and wind. Cables are cross-linked to withstand the demanding environment. A self-healing protective layer of benzotriazole compound is especially suitable for these cables.

The catalyst for the condensation reaction is suitably selected from carboxylates of metals, such as tin, zinc, iron, lead and cobalt; and a titanium compound bearing a group hydrolyzable to a Bronsted acid, between organic bases; between inorganic acids; and between organic acids; most suitably between metal carboxylates, such as tin, zinc, iron, lead and cobalt, and titanium compounds having a group hydrolyzable to a Bronsted acid, as defined above, and organic acids. The catalyst for the condensation reaction is suitably an acid, more suitably a Bronsted acid. In an even more suitable embodiment, the catalyst for the condensation reaction is a sulfonic acid, even more suitably an aromatic organic sulfonic acid, which is an organic sulfonic acid comprising the structural element:

Ar (SO3H) x (III)

in which

Ar is an aryl group that may be substituted or unsubstituted, and if it is substituted, then suitably with at least one hydrocarbyl group of up to 50 carbon atoms, and x is at least 1; or a precursor of the sulfonic acid of formula (III) including an acid anhydride thereof or a sulfonic acid of formula (III) that has been provided with hydrolyzable protecting groups, for example, an acetyl group that can be removed by hydrolysis. Said organic sulfonic acids are disclosed, for example, in Patent EP736065, or alternatively, in Patents EP1309631, EP1309632.

In one embodiment, the catalyst for the condensation reaction is an aromatic sulfonic acid, more suitably the aromatic organic sulfonic acid of formula (III). Said sulfonic acid of formula (III) as the catalyst of the condensation reaction can comprise the structural unit, according to formula (III), one or several times, for example, two or three times (as a repeating unit (II)) . For example, two structural units, according to formula (III), can be joined together by a bridging group, such as an alkylene group. Suitably the organic aromatic sulfonic acid of formula (III) has 6 to 200 carbon atoms, more suitably 7 to 100 carbon atoms.

Suitably x is 1, 2 or 3, and more suitably x is 1 or 2. Most suitably, Ar is a phenyl group, a naphthalene group, or an aromatic group comprising three fused rings such as phenanthrene and anthracene.

Examples of even more suitable sulfonic acid compounds of formula (II), which are not limiting, are p-toluenesulfonic acid, 1-naphthalenesulfonic acid, 2-naphthalenesulfonic acid, acetyl p-toluenesulfonate, acetylmethane sulfonate, dodecylbenzenesulfonic acid, octadecanoylmethanesulfonate, and tetrapropylbenzenesulfonic acid; that each, independently, may be further substituted.

The still more suitable sulfonic acid of formula (III) is substituted, that is, Ar is an aryl group that is substituted with at least one C1 to C30 hydrocarbyl group. In this most suitable subgroup of the sulfonic acid of formula (III), it is further suitable that Ar is a phenyl group and x is at least one (i.e. the phenyl is substituted with at least one -S (= O) 2OH), more suitably x is 1, 2 or 3; and more suitably, x is 1 or 2 and Ar is phenyl which is substituted with at least one C3-20 hydrocarbyl group. The most convenient sulfonic acid (III) as the catalyst for the condensation reaction is tetrapropylbenzenesulfonic acid and dodecylbenzenesulfonic acid, more suitably dodecylbenzenesulfonic acid.

The amount of the catalyst for the condensation reaction is usually 0.00001 to 0.1 mol / kg of polymer composition, suitably 0.0001 to 0.01 mol / kg of polymer composition, more suitable, 0.0005 to 0.005 mol / kg of polymer composition. The choice of catalyst for the condensation reaction and the feasible amount thereof depends on the end application and is within the skills of one of ordinary skill in the art.

In one embodiment the cable comprising the polymeric layer is an insulation layer comprising the polymeric composition. Suitably, the polymer composition is crosslinked by condensation reaction, suitably, with a condensation reaction catalyst, such as in any of the embodiments described above. The hot elongation of the crosslinked polymer composition is suitably less than 175% after 7 days at ambient conditions, HR50, more suitably less than 100%. The hot elongation is measured as described in the test procedures. An object of the present invention is good discoloration properties while maintaining good crosslinking properties, even for acid condensation reaction catalysts, such as sulfonic acids.

In one embodiment the condensation reaction is carried out using a condensation reaction catalyst which is acidic, or more suitably sulfonic acid, the amount of benzotriazole compound in the polymer composition is suitably 50 ppm to 500 ppm in the polymer composition, more suitably 50 ppm to 400 ppm, or most suitably 100 ppm to 300 ppm. It is surprising that these good crosslinking properties can be maintained with such a high loading of the benzotriazole compound, due to its basic nature.

The polymeric composition can contain one or more additional components, such as one or more other polymeric components, such as one or more miscible thermoplastics; one or more additives, such as one or more antioxidants, one or more additional stabilizers, for example, one or more hygroscopic tree retardants; one or more lubricants, one or more foaming agents, or one or more colorants; one or more charges, such as conductive charges.

The total amount of the additional polymer component (s), if present, is usually up to 30% by weight, suitably up to 20% by weight, suitably up to 10% by weight, more suitably , 0.5 to 7% by weight, based on the total amount of the polymer composition.

The total amount of the additive (s), if present, is generally 0.01 to 10% by weight, suitably 0.05 to 7% by weight, more suitably 0.2 to 5%. % by weight, based on the total amount of the polymer composition.

Suitably, the polymer composition comprises a polyolefin, a benzotriazole compound of formula (I) and optionally, and suitably, additional additives, suitably, consist thereof.

Suitably, the benzotriazole compound is added to the polymer composition in the form of a masterbatch (MB), which comprises the benzotriazole compound together with a carrier medium. Alternatively, the benzotriazole compound can be soaked in the polymer composition or the catalyst masterbatch from the condensation reaction. Most suitably, the benzotriazole compound is added as a master mix, as this makes dosing more accurate. This reduces the risk of overdose and consequently reduces the risk of impairing cross-linking. Suitably, the benzotriazole compound is added to the catalyst master mix of the condensation reaction.

In one embodiment of the present invention, the insulation layer is lined with a cover layer. Said layer is a covering layer that covers and mechanically protects the insulation layer. The purpose of such a coating is to be tough and resistant to mechanical damage, both short-term during installation and long-term after installation.

Suitably, the cable is a power cable, more suitably, it is a low voltage (LV) or medium voltage (MV) power cable, more suitably a low voltage power cable. Power cord is defined as a power transfer cord that operates at any level of power. voltage. The low voltage power cable normally operates at voltages below 6 kV, generally above 400V. MV power cables operate at higher voltage levels and in different applications than LV cables. Generally, a typical MV power cable operates at voltages from 6 to 36 kV. The low voltage power cable and, in some embodiment, the medium voltage (MV) power cables comprise an electrical conductor that is coated with a layer of insulation or a combined layer of insulation and sheath, suitably, a layer of isolation. Typically MV power cables comprise a conductor surrounded by at least an inner semiconductor layer, an insulation layer, and an outer semiconductor layer, in that order. Suitably, the cable insulation is extruded onto the copper conductor.

The present invention further relates to a method for passivating a copper conductor of a cable by migration, in which the method comprises the steps of producing a cable layer, according to any of the previous embodiments, for the addition of a passivating copper in a cable, suitably a layer of insulation. The copper conductor must be cleaned properly. The polymer composition must be applied directly to the copper conductor, suitably, by extrusion. The copper passivant migrates from the insulation layer to the copper conductor. Copper passivator is an additive that prevents copper degradation, that is, discoloration. The passivator is forming a polymeric layer on the surface, thereby protecting the copper from degradation. Suitably, the copper passivator is a benzotriazole compound, as described in any previous embodiment.

Test procedures

a) Flow rate

The MFR2 melt index was measured according to ISO 1133 at 190 ° C and a load of 2.16 kg for ethylene homopolymers and copolymers.

b) Density: Density was measured according to ISO 1183D and ISO1872-2 for sample preparation. c) The content (% by weight and% molar) of polar comonomer present in the polymer and the content (% by weight and% molar) of units containing silane groups (preferably, the comonomer) present in the polymeric composition (preferably, on the polymer):

Quantitative nuclear magnetic resonance (NMR) spectroscopy was used to quantify the comonomer content of the polymer in the polymer composition.

Quantitative 1H NMR spectra were recorded in solution state using a Bruker Avance III 400 NMR spectrometer operating at 400.15 MHz. All spectra were recorded using a standard broadband reverse 5 mm probe head at 100 ° C using nitrogen gas for all pneumatic components. Approximately 200 mg of material was dissolved in 1,2-tetrachloroethane-d2 (TCE-d2) using ditert-butylhydroxytoluene (BHT) (CAS 128-37-0) as stabilizer. Standard single pulse excitation was used using a 30 degree pulse, a 3 s relaxation delay, and no sample rotation. A total of 16 transients per spectrum were acquired using 2 simulated scans. A total of 32k data points were collected per FID with a dwell time of 60 µjs, which corresponded to a spectral window of approximately 20 ppm. The FID was filled in with zero values at 64k data points and an exponential window function with 0.3 Hz line spread was applied. This configuration was chosen primarily for the ability to resolve quantitative signals resulting from the copolymerization of methylacrylate and vinyltrimethylsiloxane, when present in the same polymer.

Quantitative 1H NMR spectra were processed, integrated, and quantitative properties determined using custom spectral analysis automation programs. All chemical shifts were internally referenced to the residual signal of protonated solvent at 5.95 ppm. When characteristic signals were presented resulting from the incorporation of vinyl acrylate (VA), methyl acrylate (MA), butyl acrylate (BA) and vinyltrimethylsiloxane (VTMS), in various comonomer sequences (Randell89). All comonomer contents were calculated with respect to all other monomers present in the polymer.

The incorporation of vinyl acrylate (VA) was quantified using the integral of the signal at 4.84 ppm assigned to the * VA sites, representing the reporter nuclei per comonomer and correcting for the overlap of the OH protons of BHT when present:

VA = (I * VA - (I ArBHT / 2) / 1

The incorporation of methyl acrylate (MA) was quantified using the integral of the signal at 3.65 ppm assigned to the 1Ma sites, which represents the number of reporter nuclei per comonomer:

MA = I 1MA / 3

Butyl acrylate (BA) incorporation was quantified using the integral of the signal at 4.08 ppm assigned to the 4BA sites, which represents the number of reporter nuclei per comonomer:

BA = I4BA / 2

The incorporation of vinyltrimethylsiloxane was quantified using the integral of the signal at 3.56 ppm assigned to the 1VTMS sites, which represents the number of reporter nuclei per comonomer:

VTMS = I 1VTMS / 9

The characteristic signals resulting from the additional use of BHT as a stabilizer were observed. The BHT content was quantified using the integral of the signal at 6.93 ppm assigned to the ArBHT sites, which represents the number of reporter nuclei per molecule:

BHT = I ArBHT / 2

The ethylene comonomer content was quantified using the integral of the major (overall) aliphatic signal between 0.00 and 3.00 ppm. This integral may include the 1VA (3) and aVA (2) sites of isolated vinyl acetate incorporation, the * MA and aMA sites of isolated methylacrylate incorporation, sites 1BA (3), 2BA (2), 3BA (2), * BA (1) and aBA (2) from isolated butyl acrylate incorporation, * VTMS and aVTMS sites from isolated vinyl silane incorporation, and aliphatic BHT sites, as well as polyethylene sequence sites . The total ethylene comonomer content was calculated as a function of the general integral and compensating for the observed comonomer and BHT sequences:

E = (1/4) * [I General -5 * VA - 3 * MA - 10 * BA - 3 * VTMS - 21 * BHT] Note that half of the signals in the overall signal represent ethylene and no comonomer and that negligible error is introduced due to the inability to compensate for the two saturated chain ends (S) without associated branching sites. The total mole fractions of a given monomer (M) in the polymer were calculated as:

fM = M / (E VA MA BA VTMS)

Total comonomer incorporation of a given monomer (M) in mole percent was calculated from mole fractions in the standard way:

M [mole%] = 100 * fM

The total comonomer incorporation of a given monomer (M) in weight percent (weight%) was calculated from the mole fractions and the monomer molecular weight (MW) in the standard way:

M [% by weight] = 100 * (fM * MW) / ((fVA * 86.09) (fMA * 86.09) (fBA * 128.17) (fVTMS * 148.23) ((1 - fVA - fMA-fBA - fVTMS * 28.05))

randall89

J. Randall, Macromol. Sci., Rev. Macromol. Chem Phys. 1989, C29, 201.

It is apparent to one skilled in the art that the above principle can be similarly adapted to quantify the content of any additional polar comonomer (s), other than MA, BA and VA, if they fall within the definition of the polar comonomer, as given in the present specification, and to quantify the content of any other units containing silane groups other than VTMS, if it falls within the definition of units containing silane groups, as given in the present specification , using the integral of the respective characteristic signal.

d) Gel content (% by weight): measured according to ASTM D2765-90 standard using a sample consisting of said silane cross-linked polyolefin polymer composition of the present invention (Procedure A, decalin extraction). The ambient conditions are 23 ° C, 50% ambient humidity (RH). The RH from 50 ° C to 100 ° C was approximately 10%, unless otherwise specified.

e) Hot elongation

Tape preparation: blends are extruded at 190 ° C. Subsequently, crosslinking is carried out in a water bath at temperatures of 90 ° C for 24 hours. The samples are then placed in a constant environment set at 23 ° C and 50% humidity for 24 h (defined as ambient conditions). Subsequently, the tapes are cut to the desired length.

The tapes described above are used to determine hot elongation properties. Three halter samples, taken along the extrusion direction according to ISO527 5A, are prepared from the 1.8 / -0.1 mm thick cross-linked tape. Hot elongation tests are performed according to EN60811-2-1 (hot elongation test) by measuring thermal deformation. The reference lines are marked 20 mm apart on the dumbbell specimens. Each test sample is fixed vertically from the upper end of it in the oven and the 0.2 MPa load is attached to the lower end of each test sample. After 15 minutes, 200 ° C in the oven, the distance between the pre-scored lines is measured and the percent elongation hot is calculated as% elongation. For% permanent elongation, the tensile force (weight) is removed from the test specimens and subsequently recovered at 200 ° C for 5 minutes and then allowed to cool to room temperature.

The% permanent elongation reported in Table 3 is calculated from the distance between the marked lines. The average of the three trials is reported.

Materials

LE4423, VTMS Ethylene Copolymer is manufactured in a high pressure radical process, in which ethylene monomers were reacted with amounts of vinyltrimethoxysilane (VTMS) to produce 1.35% by weight silane content in the copolymer . The MFR2 is 1 g / 10 min. LE4423 is disclosed in Patent EP2562768.

CatMB SA, Master Mix of Condensation Reaction Catalyst with Low Density Ethylene Polymer Vehicle (MFR2 is 7.5 g / 10 min) containing 1.5% by weight of dodecylbenzenesulfonic acid as reaction catalyst of condensation and 2% of Irganox 1010 as stabilizer, was mixed dry with the silane copolymers.

CATMB SB, Catalyst Master Mix from Condensation Reaction with Low Density Ethylene Polymer Vehicle (MFR2 is 7.5 g / 10 min) containing 4% by weight of Nacure CD-2180, supplied by King Industries as a catalyst for the condensation reaction and 2% Irganox 1010 as a stabilizer, it was mixed with dry in the silane copolymers.

CATMB Tin, catalyst masterbatch from the condensation reaction with a low density ethylene polymer carrier (MFR2 is 7.5 g / 10 min) containing 3% by weight of dioctyltin dilaurate, DOTL, as a catalyst for the condensation reaction and 2% Irganox 1010 as stabilizer, was dry mixed with the silane copolymers.

Irgamet 39 supplied by Basell, CAS 80584-90-3

Preparation of sample

Before extrusion, the copper conductors were cleaned with a cloth soaked in isopropanol. The appearance of the surface of the copper conductor was bright without defects or discoloration. Insulations were extruded onto stranded copper conductors in a mini cable line using a temperature profile of 150 ° C / 160 ° C / 170 ° C and 50 rpm. The diameter of the copper conductor was 5 mm and the thickness of the insulation layer was 0.7 mm. Furthermore, the copper conductor was preheated to 110 ° C before extrusion.

All examples have 5% by weight Condensation Reaction Catalyst Master Mix (CatMB) and 95% by weight LE4423. The Irgamet 39 was added in the CatMB. The final amount of Irgamet 39 in the polymer composition is indicated in each example.

The cables were inspected after treatment in a 90 ° C water bath for 24 hours by stripping ~ 5 cm of the insulation. In general, there was some visible discoloration after the hot water bath treatment. After treatment under ambient conditions for 24 h (23 ° C, 50% RH) there were no signs of discoloration in any of the samples.

Table 1, Discoloration Appearance of Copper Conductor

Rating Appearance Comment

1 Dark discoloration Copper has a dark skin

2 Clearly discolored

3 Slight discoloration Clearly visible gray skin covering most of the copper conductor 4 Slight discoloration Some gray spots

5 Bright copper None

Table 2, copper discoloration on the cables after a bath at 90 ° C for 24 h Sample Content of Irgamet 39 Qualification

Bare wire 5

LE4423 0 ppm 3

LE4423 CATMB Tin 600 ppm 5

LE4423 CATMB Tin 0 ppm 3

LE4423 CatMB SA 0 ppm 3

LE4423 CatMB SB 0 ppm 3

LE4423 Cat MB SA 600 ppm 4

LE4423 CatMB SB 600 ppm 4

LE4423 Cat MB SA 200 ppm 4

LE4423 Cat MB SB 200 ppm 4

From table 2 it can be seen that the addition of the copper passivant Irgamet 39 will reduce the discoloration of the copper conductor after treatment in a hot water bath. The same rating for copper discoloration was obtained for both 200 ppm and 600 ppm of total Irgamet 39 concentration in the insulation. The addition of Irgamet 39 to a tin catalyzed system works very well in terms of reducing copper discoloration. This is due to little or no interaction between the copper passivant and the catalyst of the tin condensation reaction. Furthermore, it is observed that Irgamet 39 maintains its copper passivation properties even after addition to a strong acid condensation reaction catalyst, such as sulfonic acid, which will interact with the alkali copper passivator.

Table 3. Hot elongation results with 600 ppm of Irgamet 39.

LE4423 + LE4423 +

Elongation in CatMB SA CatMB SB LE4423 CatMB SA with LE4423 CatMB SB with hot 600 ppm of Irgamet 39 600 ppm of Irgamet 39 24 h, water bath a

_{90 ° C} 57% 21% 50% 22% (2 min) fast break 7 days, ambient 51% 74% Voltage break 157%

14 days, ambient 55% 61% Voltage break 73% (2 min) Rapid break

From Table 3 it can be seen that the addition of 600 ppm of Irgamet 39 to the current concentration of catalyst from the condensation reaction cannot give sufficient crosslinking reactions under ambient conditions. By reducing the concentration of Irgamet 39 to 200 ppm, satisfactory crosslinking is achieved under ambient conditions, as shown in Table 4.

Table 4. Hot elongation results in cables.

LE4423 + LE4423 + LE4423 CatMB SA with LE4423 CatMB SB with Hot Elongation CatMB SA CatMB SB 200 ppm of Irgamet 39 200 ppm of Irgamet 39 24 h, Water bath at 90 ° C 57% 21% 31% 38%

7 days, ambient 51% 74% Quick break ^{52% (2 minutes)} _{Quick break}

14 days, ambient 55% 61% Rapid break 63%

Content of gels after

24 h, 90 ° C water bath ^{72% 70% 77%}

Gel content after

4 weeks, environment ^{70% 60% 69%}

To conclude on the environmental crosslinking by adding 200 ppm of Irgamet 39 to a sulphonic acid-based condensation reaction catalyst, measurements of gel content are also presented in Table 4. The results clearly show that sufficient crosslinking levels are achieved both after hot water bath treatment and under ambient conditions.

The Cat MB SA granules with 4,000 ppm of Irgamet 39 were sealed in an aluminum bag and stored in the oven at 50 ° C for 7 days. It is evident that the Irgamet 39 has not been migrating to the surfaces of the granules, since the granules flow freely (no sticky surface).

This allows for adequate mixing of the base resin granules and the catalyst master mix granules from the condensation reaction prior to cable extrusion.

Claims (12)

1. Cable comprising a copper conductor and a polymeric layer adjacent to the copper conductor, wherein the polymeric layer comprises a polymeric composition comprising an ethylene polymer, comprising a comonomer with silane group-containing units that are hydrolyzable, and a benzotriazole compound. 2. Cable according to claim 1, in which the benzotriazole is a compound of formula (1)

wherein R1 is a hydrogen atom, or an alkyl group comprising at least 6 carbon atoms, suitably at least 12 carbon atoms, and R2 is a hydrogen atom or an alkyl group, of suitably a methyl group. 3. Cable according to claim 2, wherein in the benzotriazole compound of formula (1) R1 comprises at least one amine group. Cable according to any of claims 1 to 3, in which the benzotriazole compound of formula (1) is a mixture of 2 isomers: N, N-bis (2-ethylhexyl) -4-methyl-1H-benzotriazole -1-methylamine (CAS No.: 80584-90-3) and N, N-bis (2-ethylhexyl) -5-methyl-1H-benzotriazole-1-methylamine (CAS No.: 80595-74-0). 5. Cable according to any of the preceding claims 1 to 4, wherein the benzotriazole compound of formula (1) is present in the polymeric composition in an amount of 50 ppm to 500 ppm. Cable according to any one of claims 1 to 5, wherein the ethylene polymer is manufactured in a high pressure radical polymerization process. 7. Cable according to any of claims 1 to 6, wherein the polymeric layer is an insulating layer comprising the polymeric composition in which the polymeric composition is cross-linked by a condensation reaction of the ethylene polymer with a comonomer with units containing silane groups. 8. Cable according to claim 7, wherein the condensation reaction is carried out using a condensation reaction catalyst which is acid, suitably an aromatic sulfonic acid. 9. Cable according to claim 7 or 8, wherein the hot elongation of the cross-linked polymeric composition in the insulation layer is less than 175% after 7 days at ambient conditions, ^h R50. Cable according to any one of the preceding claims 1 to 9, wherein the insulation layer is covered with a covering layer. A cable according to any of the preceding claims 1 to 10, wherein the cable is a power cable and suitably a low voltage power cable. 12. Procedure for passivating a copper conductor of a cable by migration, in which the procedure comprises the steps of - produce a layer of cable, according to any of claims 1 to 11 above. REFERENCES CITED IN THE DESCRIPTION This list of references cited by the applicant is solely for the convenience of the reader. They are not part of the European Patent document. Even taking into account that the compilation of the references has been done with great care, errors or omissions cannot be ruled out; EPO disclaims all liability in this regard. Patent documents cited in description • US 6262151 B EP 736065 A • WO 2014177153 A1 EP 1309631 A • JP S4910943A EP 1309632 A • CN 102969948 A EP 2562768 A • EP 1309632 B1 Non-patent literature cited in description • Encyclopedia of Polymer Science and Engineering. • CHEMICAL ABSTRACTS, 128-37-0 1986, vol. 6, 383-410 • J. RANDALL. Macromol. Sci., Rev. Macromol. Chem. • Polyethylene: High-pressure. R.KLIMESCH; Phys, 1989, vol. C29, 201 D.LITTMANN; F.-O. MÁHLING. Encyclopedia of Materials: Science and Technology. Elsevier Science Ltd, 2001,7181-7184